<html>
<body>
Xiaobing,<br><br>
There are at least 2 issues here:<br><br>
1) TMYs are selected to be representative of long term conditions and are
generally used for energy calculations, not sizing. In theory, the
TMY year has about the same overall distribution of some combined
statistic as does the 30 year record. However, that does not
guarantee representative distribution of dry-bulb temperature, coincident
dry-bulb / wet-bulb, etc. There is probably an OK match, but to my
knowledge there has not been a systematic study of how good the match
is. So there is a risk.<br><br>
2) A completely separate issue is use of real day sequences for loads
calcs. ASHRAE loads methods (Heat Balance, RTS) simulate the design
day over and over. Thus the design condition is equivalent of a
long sequence of hot, sunny days with the building fully occupied.
No cooler days, no weekends. Depending on the climate and the
building, a real day sequence simulation will predict lower peaks, often
much lower. If the right sequence is used, this result might be
more realistic. But selecting the right sequence is tricky.
For the present, the conservative approach is to avoid the problem and
repeat the design day.<br><br>
TC 4.2 has sponsored research to support a possible transition to
real-sequence design procedures --<br><br>
<h3>Colliver et al. 1998. Sequences of Extreme Temperature
and Humidity for Design Calculations. 828-RP. This project
produced the "</h3>Design Weather Sequence Viewer" CD-ROM
available from the ASHRAE bookstore.<br><br>
<h2>Klein and </h2>Reindl. 2000. <h2>Automated Generation of
Hourly Design Sequences. 962-RP. This project produced
"EXTREMES: Weather Sequence Generator" CD-ROM available from
the ASHRAE bookstore.<br><br>
These projects may have been a bit ahead of their time. As
simulation becomes more mainstream, real-sequence loads calcs may move
into practice. A very interesting project would be a comparison of
equipment sizing results using traditional design-days, TMYs, and
synthetic sequences (e.g. EXTREMES), and real sequences.<br><br>
Chip Barnaby</h2>At 05:51 PM 3/21/2007, Xiaobing Liu wrote:<br>
<blockquote type=cite class=cite cite=""><font size=2 color="#0000FF">
Dear all:<br>
</font> <br>
<font size=2 color="#0000FF">I'm looking for information regarding the
uncertainty of using TMY2 weather data in the simulation for sizing HVAC
equipment. Does anyone know anything about this? Thanks,<br>
</font> <br>
<font size=2 color="#0000FF">Xiaobing<br>
</font><br>
<pre>
You received this e-mail because you are subscribed
to the BLDG-SIM@GARD.COM mailing list. To unsubscribe
from this mailing list send a blank message to
BLDG-SIM-UNSUBSCRIBE@GARD.COM
</pre><font face="Courier New, Courier"></blockquote>
<x-sigsep><p></x-sigsep>
---------------------------------------------------------<br>
Chip
Barnaby
cbarnaby@wrightsoft.com<br>
Vice President of Research<br>
Wrightsoft
Corp.
781-862-8719 x118 voice<br>
394 Lowell St, Suite 12
781-861-2058 fax<br>
Lexington, MA
02420
<a href="http://www.wrightsoft.com" eudora="autourl">
www.wrightsoft.com<br>
</a>---------------------------------------------------------</font>
<PRE>
======================================================
You received this e-mail because you are subscribed
to the BLDG-SIM@GARD.COM mailing list. To unsubscribe
from this mailing list send a blank message to
BLDG-SIM-UNSUBSCRIBE@GARD.COM
</PRE></body>
</html>